Biomedical subjects

Penny Theodorou

Publications and source records attributed to Penny Theodorou.

5 recordsLinked to original sources

PubMed2006

Examining the association between blood manganese and lead levels in schoolchildren in four selected regions of South Africa.

This study assessed the possibility of relationship between manganese and lead levels in blood in schoolchildren residing in different geographical regions of South Africa. A cross-sectional survey was carried out in schools of three cities: Cape Town (11 schools), Johannesburg (10 schools), Kimberley (six schools) and in the Northern Cape in three rural sites (four schools). A total of 1282 venous blood samples were collected from grade one children. The relationships between blood manganese and blood lead levels (treating each in turn as the response variable in order to adjust for the effect of confounding variables) were investigated by fitting mixed models. Mixed models were fitted with natural log (manganese concentration) as the response variable, and blood lead level as the principal explanatory factor. The model also included terms for centre and a centre by lead interaction and examined potential confounders. The important confounders were found to be gender, race and whether there was paint peeling from the outside walls. There was a significant centre by lead interaction (P<0.0001) with the effect of lead on ln(Mn) being different in the various centres. Mixed models fitted with blood lead level as the response variable and blood manganese as the principal explanatory factor, with terms for centre, a centre by manganese interaction and potential confounders, again found overwhelming evidence (P<0.0001) of a centre by manganese interaction. The study found great variability in both blood lead and manganese levels, both within and between sites, and there was not a consistent relationship between the two metals in the four sites.

Child↗

PubMed2005

Lipid peroxidation and trace elements in systemic sclerosis.

Oxidative stress appears to be important in the causation and perpetuation of tissue injury and fibrosis in systemic sclerosis or scleroderma (SSc). We conducted a case-control study to assess lipid peroxidation levels as determined by measuring fasting plasma malondialdehyde (MDA) and serum levels of the trace elements selenium, iron, zinc and copper in SSc. Plasma MDA levels were almost tenfold higher in patients than in controls (p=0.00007), and an inverse relationship between MDA levels and disease duration (r=-0.52, p=0.044) was observed. Selenium levels were lower in patients than in controls (p=0.012). Within the patient cohort, copper correlated inversely with the total skin score (r=-0.52, p=0.03). Our findings provide further evidence that lipid peroxidation is increased and antioxidant capacity is reduced in SSc. The gradual decline in MDA levels with time suggests that antioxidant therapy, if to be useful in SSc, is most likely to be effective early in the course of the disease.

Case-Control Studies↗

PubMed2005

Blood manganese concentrations among first-grade schoolchildren in two South African cities.

Little information exists on the environmental exposures to low levels of organometallic manganese (a principal combustion product from manganese-containing fuel additives) and public health. This study was undertaken to establish biological and environmental levels of manganese among first-grade schoolchildren in the South African cities of Johannesburg and Cape Town. The study was undertaken subsequent to partial introduction of the manganese-containing fuel additive methylcyclopentadienyl manganese tricarbonyl (MMT) to South African petrol in the Johannesburg region only, about 24 months prior to the commencement of the study, and in anticipation of possible future increases in MMT use in the rest of the country. This study involved the measurement of manganese concentrations in the blood of the total number of 814 of grade one schoolchildren (430 and 384 in Cape Town and Johannesburg, respectively), and in water supplies, soil, and classroom dust at a total number of 21 participating schools. The results indicated higher concentrations of manganese in school soil (P=0.0007) and dust (P=0.0071) samples from Johannesburg relative to Cape Town. Similarly, the mean blood manganese concentration in Johannesburg study subjects (9.80 microg/L, SD 3.59) was significantly higher than that in Cape Town study subjects (6.74 microg/L, SD 3.47), after allowing for the clustering effect within schools and adjusting for the confounding effect of population group (P<0.0001). The blood manganese levels of 4.2% and 12.5% of children in Cape Town and Johannesburg, respectively, equaled or exceeded 14 microg/L, the upper normal reference value specified by the Agency for Toxic Substances Disease Registry (ATSDR, 2000). Importantly, levels of manganese in blood were found to be significantly associated with concentrations of manganese in classroom dust at schools.

Child↗

PubMed2003

Nervous system effects of occupational manganese exposure on South African manganese mineworkers.

Occupational exposure to airborne manganese dust has been shown to produce adverse effects on the central nervous system. Four hundred and eighty-nine blue and white collar manganese mineworkers from South Africa were studied cross-sectionally to investigate the nervous system effects of medium to low occupational manganese exposures. The different facilities included underground mines, surface processing plants, and office locations. A job exposure matrix was constructed using routine occupational hygiene data. Exposure variables included years of service, a cumulative exposure index (CEI) and average intensity of exposure (AINT) across all jobs, and blood manganese. Endpoints included items from the Q16, WHO-NCTB, SPES, and Luria-Nebraska test batteries, and a brief clinical examination. Potential confounders and effect modifiers included age, level of education, past medical history including previous head injury, previous neurotoxic job exposures, tobacco use, alcohol use and home language. Associations were evaluated by multiple linear and logistic regression modeling. Average exposure intensity across all jobs was 0.21mg/m(3) manganese dust. Multivariate analyses showed that none of the symptom nor test results were associated with any measure of exposure including blood manganese, after adjustment for confounders. This relatively large null study indicates that manganese miners exposed on average across all jobs to MnO(2) at levels near the American Conference of Governmental Industrial Hygienists Threshold Limit Value (ACGIH TLV) are unlikely to have a subclinical neurotoxicity problem.

Adult↗

PubMed2003

The utility of biological monitoring for manganese in ferroalloy smelter workers in South Africa.

Five hundred and nine workers at a manganese (Mn) smelting works comprising eight production facilities and 67 external controls were studied cross-sectionally. Exposure measures from personal sampling included inhalable dust, cumulative exposure indices (CEI) and average intensity (INT = CEI/years exposed) calculated for the current job at the smelter and also across all jobs held by subjects. Biological exposure was measured by Mn in the blood (MnB) and urine (MnU) and biological effect was measured by serum prolactin. Average lifetime exposure intensity across all jobs ranged from near 0 (0.06 microg/m3) for unexposed external referents to 5 mg/m3. Atmospheric exposures and MnB and MnU distributions were consistent with published data for both unexposed and smelter workers. Associations between biological exposures and groups defined by atmospheric exposures in the current job were substantial for MnB, less so for MnU and absent for serum prolactin. Random sampling of MnB measurements representative of a group of workers with more than 1-2 years of service in the same job and notionally homogenous exposure conditions could serve as a cross-sectional predictor of atmospheric Mn exposure in the current job, as well as for surveillance of Mn exposure trends over time. Correlations at the individual level were only modest for MnB (33% of the variance in log atmospheric Mn intensity in the current job was explained by log MnB), much worse for MnU (only 7%). However, a receiver operating characteristic (ROC) analysis was performed which showed that it is possible to use a MnB cut-off of 10 microg/l (the 95th percentile in the unexposed) to good effect as a screening tool to discriminate between individual exposures exceeding and falling below a relatively strict atmospheric Mn exposure threshold at the ACGIH threshold limit value (TLV) of 0.2 mg/m3. MnU has no utility as a measure of biological exposure nor does serum prolactin as a measure of biological effect.

Alloys↗